1. Field of the Invention
This invention relates to equipment for applying double-ended flexible plastic labels to round containers, such as bottles and cans, on a high-speed production basis.
2. Description of the Prior Art
U.S. Pat. No. 4,323,416 (Malthouse et al.) discloses equipment for applying double-ended labels from a web or strip of such labels to bottles. This equipment is provided with an adhesive applicator to apply an adhesive substance to the label, after the label has been severed from the web or strip and before the label is applied to the bottle, to ensure adhesion of the label to the bottle. The adhesive usually used in bottle labeling equipment of this type is a hot-melt adhesive, and the use of such a hot-melt adhesive is messy and can be expensive because of the cost of the adhesive and the cost of equipment for storing it, handling it, and applying it. Further, the use of a hot-melt adhesive system leads to a high temperature environment near the labeling machine which is uncomfortable for the operator and which requires special safety precautions for the proper operation and servicing of the machine. U.S. Pat. No. 4,406,721 (Hoffman) also discloses a system for applying double-ended labels from a web of such labels to bottles or other containers. The system of Hoffman utilizes heat to cause the labels to shrink after they have been applied to the bottles. United States Patent 3,235,433 (Cvacho, et al.) describes a similar system in which a heat-activatable adhesive that is pre-applied to the label is heat activated before the label is applied to the container.
U.S. Pat. No. 4,574,020 (Fosnaught), which is assigned to the assignee of this application, the disclosure of which is hereby incorporated by reference herein, recognized the objection to the use of a hot-melt adhesive in a container labeling system, especially in regard to a container labeling system that utilizes labels formed from thermoplastic materials. The invention described in the aforesaid U.S. Pat. No. 4,574,020 eliminated the need for an applicator to apply a hot-melt adhesive to the label being applied to the bottle by utilizing a gravure roll applicator to apply an unheated solvent to the label to permit the label to adhere to the bottle, the solvent being a solvent at least for the thermoplastic material in the label, for example, methylene chloride as a solvent for labels formed from polystyrene, thereby eliminating some of the disadvantages inherent in utilizing a hot-melt adhesive in a bottle labeling system.
In the operation of the system disclosed in the aforesaid U.S. Pat. No. 4,574,020, one of the most critical aspects is the precise transfer of the solvent from the gravure roll to the surface of the label. If the gravure roll surface and the label surface do not make proper contact, there will not be sufficient solvent applied to the leading edge of the label in order to dissolve the desired portions of the label so as to make it adhere to the bottle or container as it comes into contact therewith and transfers thereto. Likewise, as the label trailing edge overlaps the leading edge, it is absolutely necessary that a full height strip of solvent be applied to the trailing edge so that a complete overlap seam will be formed. This seam must be complete since some subsequent heat shrinkage of the label about the bottle will open the seam up and produce a defective or distorted label if the seam is not sealed throughout its full height.
The label is carried by a rotatable vacuum drum which has sets of raised areas or pads on its periphery that underlie the leading and trailing edges of the label, and the rotating gravure roll is set to engage these raised critical portions of the label during the rotation of the vacuum drum and the gravure roll relative to one another. The gravure roll is normally mounted on a platform which is shiftable about a vertical axis that is parallel to the axis of the roll. In order to ensure that the solvent is properly applied, the gravure roll must carry a sufficient quantity of solvent on its surface pattern. The use of a vertical fountain biased against the gravure to apply solvent to the gravure roll is shown in the aforesaid U.S. Pat. No. 4,574,020. However, the fountain disclosed in this patent requires considerable down time in order to remove the fountain, and it frequently is necessary to remove a fountain to repair a jam up in the labeling machine or to change fountains as they become worn or become contaminated with extraneous materials.